Strong to weak localization transition and two-parameter scaling in a two-dimensional quantum dot array

Abstract

The transition from strong to weak localization behavior was observed in two-dimensional Ge/Si quantum dot structure under the variation in the quantum dot occupancy, their areal density and annealing of the structures at 480-625°C. To clarify the carrier transport mechanism and separate the hopping and diffusive regimes, the temperature dependence of conductance and conductance nonlinearity were analyzed in the structures with different correlations between the disorder and interaction. It was shown that the change in the relative disorder without significantly changing the interaction keeps the system inside the one-parameter scaling. The role of the interaction in two-parameter scaling was revealed by observing the shift of Gell-Mann-Low scaling function for the samples with large variation in the Coulomb interaction.

Magnetoresistance in two-dimensional array of Ge/Si quantum dots

“…Results and discussions 3.1. Temperature dependence of conductance Fig 1a. demonstrates the temperature dependence of sheet conductance as Arrhenius plots for the following samples: for SD samples with filling factor ν ≈2.4 annealed at different temperatures (number 2-6), for SD sample with ν ≈2 annealed at 550 • C (7) and for the sample with double density of dots (ν ≈3) in zero magnetic field (1). One can see that the conductance strongly depends on sample parameters and changes by the several order of magnitude.…”

“…Our previous study of temperature dependence of conductance and its non-linearity in 2D Ge/Si quantum dot (QD) array [1] showed that change of the structural parameters of the system results in the transition from strong (SL) to weak localization (WL) behavior and, respectively, from hopping to diffusive transport. Different transport regimes should be characterized by different behavior of magnetoresistance (MR).…”

Electron localization in self-assembled Si quantum dots grown on Ge(111)

“…Analysis of the low temperature parts (<10 K) shows that the temperature dependencies of conductance for both samples are described by ES law confirmed the strong carriers localization in the structure under study. The small temperature of the transition from the band to hopping transport, as compared to Ge/Si QDs structures [30], is explained by smaller ionization energy of Sb in Ge than in Si.…”

“…• C temperatures resulted in a considerable increase of the conductance up to the observation of transition from hopping to the diffusion regime [30]. This was explained by smoothing of the localization potential and the corresponding increase of the wave functions overlapping due to a smearing of the QDs caused by Ge-Si intermixing.…”

“…It was previously shown [30] that the lateral transport in two-dimensional Ge QD array with QD sizes and density similar to the Si QD system under study is described by variable range hopping via strong localized QD states taking into account long-range Coulomb interaction (Efros-Shklovskii (ES) law [31]). To confirm the strong electron localization in Si QDs and check whether the mechanism of electron transport in Si QD samples is similar to the hole transfer in Ge QD samples, the temperature dependence of conductance, magnetoresistance (MR) and photoconductance were studied.…”